might have fixed some of the boot_drive issues with ext_read

bochsrc.bxrc

@@ -1,20 +1,18 @@
 # configuration file generated by Bochs
-plugin_ctrl: voodoo=false, unmapped=true, biosdev=true, speaker=true, extfpuirq=true, parallel=true, serial=true, busmouse=false, e1000=false, es1370=false, gameport=true, ne2k=false, sb16=false, usb_uhci=false, usb_ohci=false, usb_ehci=false, usb_xhci=false
+plugin_ctrl: voodoo=false, unmapped=true, biosdev=true, speaker=true, extfpuirq=true, parallel=true, serial=true, busmouse=false, e1000=false, es1370=false, gameport=true, iodebug=true, ne2k=false, sb16=false, usb_uhci=false, usb_ohci=false, usb_ehci=false, usb_xhci=false
 config_interface: win32config
 display_library: win32
 memory: guest=64, host=64, block_size=128
-romimage: file="C:\Program Files\Bochs-2.8\BIOS-bochs-latest", address=0x00000000, options=none, flash_data=none
+romimage: file="C:\Program Files\Bochs-2.8\BIOS-bochs-legacy", address=0x00000000, options=none, flash_data=none
 vgaromimage: file="C:\Program Files\Bochs-2.8\VGABIOS-lgpl-latest"
 boot: disk
-floppy_bootsig_check: disabled=0
+floppy_bootsig_check: disabled=1
 floppya: type=1_44
 # no floppyb
 ata0: enabled=true, ioaddr1=0x1f0, ioaddr2=0x3f0, irq=14
-ata0-master: type=disk, path=".\disk.img", mode=flat, cylinders=0, heads=0, spt=0, sect_size=512, model="Stevia Disk", biosdetect=auto, translation=lba
+ata0-master: type=disk, path=".\disk.img", mode=flat, cylinders=0, heads=16, spt=63, sect_size=512, model="Stevia Disk", biosdetect=auto, translation=auto
 ata0-slave: type=none
-ata1: type=none
-ata1-master: type=none
-ata1-slave: type=none
+ata1: enabled=false
 ata2: enabled=false
 ata3: enabled=false
 optromimage1: file=none
@@ -29,7 +27,10 @@ pci: enabled=1, chipset=i440fx, slot1=none, slot2=none, slot3=none, slot4=none,
 vga: extension=vbe, update_freq=10, realtime=1, ddc=builtin
 cpu: count=1, ips=1000000, model=p3_katmai, reset_on_triple_fault=1, cpuid_limit_winnt=0, ignore_bad_msrs=1, mwait_is_nop=0
 print_timestamps: enabled=0
-port_e9_hack: enabled=false, all_rings=false
+debugger_log: -
+magic_break: enabled=1
+port_e9_hack: enabled=true, all_rings=false
+iodebug: all_rings=0
 private_colormap: enabled=0
 clock: sync=none, time0=local, rtc_sync=0
 # no cmosimage
@@ -43,9 +44,9 @@ keyboard: type=mf, serial_delay=150, paste_delay=100000, user_shortcut=none
 mouse: type=none, enabled=false, toggle=ctrl+mbutton
 sound: waveoutdrv=dummy, waveout=none, waveindrv=dummy, wavein=none, midioutdrv=dummy, midiout=none
 speaker: enabled=true, mode=sound, volume=15
-parport1: enabled=true, file=none
+parport1: enabled=false
 parport2: enabled=false
-com1: enabled=true, mode=null
+com1: enabled=false
 com2: enabled=false
 com3: enabled=false
 com4: enabled=false

include/fat32/FAT32_SYS.inc

@@ -38,8 +38,7 @@ InitFATDriver:
     sub sp, 0x6
 
 .calc_active_part:
-    mov bx, [partition_offset_ptr]
-    mov ax, word [ds:bx]                     
+    mov ax, word partition_offset            
 
     mov dx, partition_table
     add dx, ax                                                           ; dx points to the partition that was booted from
@@ -114,7 +113,7 @@ SearchFATDIR:
         add sp, 0x4
 
         cmp eax, 0x0fff_fff7
-        je SearchFATDIR.bad_cluster
+        ;je SearchFATDIR.bad_cluster            ; TODO: Implement Bad cluster checks
         jb SearchFATDIR.load_next_dir_next_OK
         ERROR STAGE2_FAT32_END_OF_CHAIN
 
@@ -234,8 +233,8 @@ NextCluster:
     add eax, ecx        ; fat_sector + first_fat_sector
     mov dword [si + FAT32_NextClusterData_t.fat_sector], eax
 .load_fat_table:
-    mov bx, word [boot_drive_ptr]
-    movzx ax, byte [ds:bx]
+    xor ax, ax
+    mov al, boot_drive
     push ax
 
     mov ax, 0x1
@@ -306,8 +305,8 @@ ReadFATCluster:
 .func:
     print_string ReadFATCluster_INFO_cstr
 
-    mov bx, word [boot_drive_ptr]
-    movzx ax, byte [ds:bx]
+    xor ax, ax
+    mov al, boot_drive
     push ax
 
     mov ax, 0x1                         ; count = 1

src/stage2/stage2.nasm

@@ -49,14 +49,18 @@
 section .text
 begin_text:
 ; dl = byte boot_drive
-; si = word part_offset (active partition offset)
-; bx = ptr PartTable_t partition_table
-; dx = ptr FAT32_bpb_t fat32_bpb
+; ax = word part_offset (active partition offset)
+; si = ptr PartTable_t partition_table
+; di = ptr FAT32_bpb_t fat32_bpb
 ALIGN 4, db 0x90
 init:
-    __BOCHS_MAGIC_DEBUG
     cli                               ; We do not want to be interrupted
 
+    mov [vbr_part_table_ptr], bx             ; pointer to partition_table
+    mov [vbr_fat32_bpb_ptr], dx              ; pointer to fat32_bpb
+    mov [boot_drive], dl                     ; copy boot_drive to globals
+    mov [partition_offset], ax               ; copy partition_offset to globals
+
     mov ax, __STAGE2_SEGMENT          ; set all our segments to the configured segment, excep es
     mov ds, ax                        ; *
     mov fs, ax                        ; *
@@ -81,7 +85,7 @@ init:
 
     mov sp, stack_top
     mov bp, sp
-    sub sp, 0x20
+    sub sp, 0x10
     push bp                           ; setup a somewhat normal stack frame, minus a ret ptr
 
     sti
@@ -121,22 +125,9 @@ struc EarlyBootStruct_t
     .fat32_ebpb      resb FAT32_ebpb_t_size
 endstruc
 
-; bp - 2 : byte boot_drive
-; bp - 4 : word part_offset
-; bp - 6 : ptr PartTable_t partition_table
-; bp - 8 : ptr FAT32_bpb_t fat32_bpb
 ALIGN 4, db 0x90
 main:
-    lea ax, [bp - 2]
-    mov [boot_drive_ptr], ax
-
-    lea ax, [bp - 4]
-    mov [partition_offset_ptr], ax      ; setup pointers to boot_drive and partition offset on stack
-
-    mov byte [bp - 2], dl               ; boot_drive (probably 0x80)
-    mov word [bp - 4], si               ; partition_offset
-    mov word [bp - 6], bx               ; partition_table
-    mov word [bp - 8], dx               ; fat32_bpb
+    __BOCHS_MAGIC_DEBUG
 .check_sig:
     mov eax, dword [STAGE2_SIG]
     cmp eax, 0xDEADBEEF
@@ -145,7 +136,7 @@ main:
 .stage2_main:
     mov ax, PartTable_t_size
     push ax
-    mov ax, [bp - 6]                                    ; ptr partition_table
+    mov ax, word [vbr_part_table_ptr]                       ; ptr partition_table
     push ax
     mov ax, partition_table                                  
     push ax
@@ -154,7 +145,7 @@ main:
 
     mov ax, (FAT32_bpb_t_size + FAT32_ebpb_t_size)         ; size in byte
     push ax
-    mov ax, [bp - 8]                                    
+    mov ax, word [vbr_fat32_bpb_ptr]                                    
     push ax
     mov ax, fat32_bpb                                       ; defined in memory.inc, destination
     push ax
@@ -503,33 +494,44 @@ section .bss follows=.sign
 begin_bss:
 ; structures
 
-align 16, resb 1
+align 8, resb 1
 partition_table resb PartTable_t_size
 
-align 16, resb 1
+align 8, resb 1
 fat32_bpb resb FAT32_bpb_t_size
 fat32_ebpb resb FAT32_ebpb_t_size
 
-align 16, resb 1
+align 8, resb 1
 fat32_nc_data resb 16
 
-align 16, resb 1
+align 8, resb 1
 lba_packet resb LBAPkt_t_size
 
-align 16, resb 1
+align 8, resb 1
 fat32_state:
     resb FAT32_State_t_size
 
-align 16, resb 1
+align 8, resb 1
 SteviaInfo:
     resd 4
 
 ;
-; locals
+; globals
 ;
-boot_drive_ptr:
+align 8, resb 1
+boot_drive:
+    resb 1
+
+align 8, resb 1
+partition_offset:
     resw 1
-partition_offset_ptr:
+
+align 8, resb 1
+vbr_fat32_bpb_ptr:
+    resw 1
+
+align 8, resb 1
+vbr_part_table_ptr:
     resw 1
 
 ;

src/vbr/vbr.nasm

@@ -152,10 +152,10 @@ main:
     call read_disk_raw
     add sp, 0xC
 .enter_stage2:
-    mov dl, byte [bp - 2]               ; boot_drive
-    mov si, word [bp - 4]               ; part_offset
-    mov bx, partition_table
-    mov dx, fat32_bpb
+    mov dl, byte [bp - 2]               ; byte boot_drive
+    mov ax, word [bp - 4]               ; word part_offset
+    mov si, partition_table             ; ptr partition_table
+    mov di, fat32_bpb                   ; ptr fat32_bpb
     jmp word 0x0000:STAGE2_ENTRY
 
 ; ###############